Well completions



NOV. 8, 1966 110, ALLEN ET AL 3,283,815

WELL COMPLETIONS Filed March 1, 1963 5 Sheets-Sheet 1 John E. Ortloff a Thomas 0. Allen INVENTORS.

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John E. Orrloff Thomas 0. Allen INVENTORS A TTORNE'Y Nov. 8, 1966 Filed March 1, 1963 Nov. 8, 1966 ALLEN ET AL WELL COMPLETIONS 5 Sheets-Sheet 4 Filed March 1, 1963 FIG.

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Thomas 0. Allen INVENTORS.

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ATTORNEY United States Patent 3,283,815 WELL COMPLETIONS Thomas 0. Allen and John E. Ortloif, Tulsa, Okla., assignors, by mesne assignments, to Esso Production Research Company, a corporation of Delaware Filed Mar. 1, 1963, Ser. No. 262,056 7 Claims. (Cl. 16627) This invention relates to methods and apparatus for completing oil wells. More particularly, the invention concerns means for casing and supporting the wall of a well opposite a producing formation.

Ordinarily, in the completion of a typical oil well, casing is cemented within the well from top to bottom and serves to support the wall of the well. It also resists any hydrostatic or other pressures that may exist in various formations encounted. In addition, it provides a continuous conduit from the top to the bottom of the well, within which one or more strings of production tubing may be suspended. The cost of the casing, in some areas, is often as high as 30% of the total cost of the well.

Improved methods of eliminating expensive casing have been and are constantly being sought by oil producers and operators. It has been found, for example, when drilling wells in areas such as West Texas that except for controlling formation pressure, no casing is needed at all. In other areas, such as employing multiple strings of small diameter casing, which are cemented in the lower part of the hole, several techniques have been suggested for stabilizing the walls of the wells to prevent caving and sloughing above the cement. Conventional bentonitic drilling muds or low fluid loss oil-base or oil-emulsion muds, for example, may be used in drilling such wells. These muds deposit a tough, stabilizing sheath on the wall of a well. Other techniques include depositing various settable synthetic resins or latex films, or simply forming a cement sheath.

Even though a well can be successively stabilized by one of the above procedures, it is still necessary in many cases that a high strength casing be positioned opposite the productive formation to permit a greater amount of control over the final completion and production of the well. In all such cases it has been the practice to case the well completely from the well head to the formation.

Accordingly, it becomes a primary object of this invention to provide a method and apparatus for completing a well without the need for installing casing throughout the well. In that regard, this invention has particular application to wells which do not need to be stabilized or which can be stabilized, where needed, to preclude the intrusion by unwanted fluids as well as the collapse or caving of the various non-oil producing formations penetrated by the well.

Another object of this invention is to provide methods and apparatus for positioning and setting a relatively short length of casing in a well opposite one or more producing formations.

These and other objects of this invention will become more apparent upon further reading of the specification and claims when taken in conjunction with the following illustrations, of which:

FIGURE 1 is a vertical elevational view, partly in crosssection, illustrating a typical well completed in a manner in accordance with this invention.

FIGURES 2 and 3 are vertical elevational views, partly in cross-section, of the lower end of the well of FIG- URE 1 adjacent at producing formation. These figures depict the steps of cementing a relatively short section of casing in a borehole and completing the well.

FIGURE 4 is a vertical elevational view, partially in cross-section, showing the application of this invention to the completion of a well having two separated productive formations.

FIGURE 5 is a vertical elevational view, partly in crosssection, of a type of latching mechanism useful in the practice of this invention to place casing in a well. The mechanism is shown in a retracted position.

FIGURE 6 is an elevational view, partly in cross-section, of the latch shown in FIGURE 5 in a locked, expanded position.

FIGURE 7 is a vertical, elevational, cross-sectional view of alternate apparatus capable of use in the practice of this invention.

FIGURE 8 depicts an alternate apparatus for positioning casing Within a well.

FIGURE 9 is a sectional view taken along the line 99 of FIGURE 8.

Broadly speaking, this invention is concerned witha method of completing wells by the placement of a relatively short, longitudinal section of casing in a well opposite one or more productive subterranean formations. The invention is also concerned with apparatus for ac complishing such a completion.

Referring to FIGURE 1, a well 10 extends from the earths surface to a hydrocarbon productive formation 12. Typical completion practices include the placement of a surface casing 14, usually required by law, which is held in place by cement 16. The well extends through various types :of formations that are prevented from sloughing or otherwise entering into the well by a stabilizing material 18 which forms a sheath on the wall of the well. Such materials and their methods of application are typically described in U.S. Patent 3,055,424, issued September 25, 1962, and co-pending application Ser. No. 11,201, filed February 26, 1960 and now Patent No. 3,126,959.

In the operation of this invention a relatively short longitudinal section of casing 20 is held in position by cement 22 opposite productive formation 12. Production tubing 24 extends from a well head 26 to a point opposite the productive formation. The production tubing is held within casing 20 by anchoring means generally designated by the legend 28. Paclooff means 30 positioned above the perforations in casing 20 seals the annulus between the tubing 24 and the casing. Pack-off means 30 is preferably located below the anchoring means. Anchoring means 28 may comprise a combination locking and sealing means if so desired.

FIGURE 2 depicts a suitable method and apparatus for placing and cementing a relatively short longitudinal section of casing 20 adjacent to a producing formation 12. Attached to the lower end of casing 20 is a special guide or cementing shoe 32 which seals the annulus between tubing 24 and the casing. In the assembled position casing 20 and tubing 24 are retained together by locking or anchoring means 28, hereinafter specifically described. In this locked condition, the casing is lowered into the borehole and cemented in place. The bottom end of tubing 24 is provided with a check valve 34 which permits cement 22, and chaser fluid 36 to be forced through the valve into the annular space be tween casing 20 and well 10 opposite formation 12.

Cement slurry 22 and chaser fluid 36 are forced through check valve 34 and into position by a conventional separator plug 38 used in cementing wells. Thereafter tubing 24 is released from casing 20 and removed with anchoring means 28 from the well. A wire line actuated casing perforating device can then be lowered into the casing opposite formation 12 to form a plurality of connecting channels or perforations 40 (FIGURE 1) between the formation and. the well. Next, after removing valve assembly 34 and plug 38, the open end roduction tubing string 24 can be locked in casing 20 with a. combination locking and sealing assembly 28 for a simple completion.

Thereafter, or in addition, other well known formation treating methods such as hydraulic fracturing, acidizing, etc. may be accomplished.

An alternate method of completion is depicted in FIG- URE 3 wherein anchoring means 28 and sealing means 30 are employed. Tubing 24 is retained within the casing by the anchoring means 28 which in this instance may again comprise a combination locking and. sealing mechanism. Below sealing means 28 and directly above perforations in producing formation 12 is located sealing means 30 which consists of a production packer shown in more detail in FIGURE 7. The packer includes a swing check valve 42 for retaining the formation pressure whenever production tubing 24 is removed from casing 20.

In this alternate method, if desired, the well may be completed using permanent type well completion techniques. The various well completion and production increasing techniques such as perforating, fracturing, acidizing, etc., are then applied to formation 12 through the tubing. For details of some permanent type well completion apparatus and techniques see US. Patents 2,749,- 989 and 2,751,009.

FIGURE 4 represents another embodiment of the invention wherein casing 20 is positioned and held by cement 22 opposite two productive formations 12A and 123 which communicate with the well by way of perforations 40A and 40B respectively. In this embodiment, adapter 44 includes means for receiving individual locking means 28 and 28 on each of two strings of production tubing 46 and 48. In addition, packer elements 50 and 52 are adapted to isolate fluid production from each of the formations.

FIGURES 5 and 6 depict in detail a suitable latching mechanism to use as an anchoring means for locking tubing 24 to casing 20. An outer sleeve member 62 is adapted to fit about tubing 24 in a movable relation. The upper end of an enlarged left-hand threaded portion of the tubing abuts against a shoulder on the outer sleeve member 62.

Included in the outer sleeve member are a resilient seal 64 and a multiplicity of longitudinal slots or openings 66. Outer sleeve member 62 is telescopically slidable with respect to an inner sleeve member 68 which is sealed with respect to tubing 24 by an O-ring or inner seal 70 and with respect to casing 20, when in its latched position, by an outer packing or seal 72.

The inner sleeve member 68 includes an upper end portion 74 within which left-hand threaded opening '76 is provided for engagement with the threaded portion 60 of tubing 24. A plurality of upper latching dogs 78 are pivoted. on inner sleeve member 68 and normally biased outward as by means of leaf springs 80. The upper ends or catch surfaces 82 of the latching dogs 78 are positionable within and operable through slots 66.

A plurality of lower dog members 84 are normally biased outward by leaf springs 86 so as .to engage with an appropriately located shoulder 88 (FIGURE 6) on casing 20 to prevent further downward movement of the tubing 24 within the casing. Upper dogs 78 are similarly adapted to prevent upward movement of the latch and tubing by engagement with shoulder 90 of the casing.

To position and lock the tubing 24 in place, left-hand threads of shoulder 60 are engaged in the threaded opening 76 of inner sleeve 68 as shown in FIGURE 6. Tubing 24 and the latching mechanism then are lowered within the casing 90 until lower dogs 84 abut against shoulder 88 (shown in FIGURE 6), and until upper latching dogs 78 are biased outwardly from outer sleeve 62 by springs 80 through slots 66 into abutting and locking engagement with shoulder 90. Hence, the latching mechanism and the tubing are restrained from any vertical movement. The tapered upper end of casing 20 permits movement of the normally outwardly biased upper latching dogs '78 and lower dogs 84 into the latched position shown in FIGURE 6.

To remove the latching mechanism, the left-hand threads are disengaged by turning the tubing. This permits outer sleeve member 62 to be raised telescopically with respect to inner sleeve member 68 whereby the lower edges of slots 66 mate with upper latching dogs 78 to retract the dogs into their appropriate recesses 79 as shown in FIGURE 5.

When a conventional production packer (shown in FIGURE 7) is installed for use with the present invention, it is positioned within the casing 20 at the desired elevation, usually a few feet above perforations 40. Typically, such a packer includes an appropriate outer sealing element and upper and lower casing holding slips 102 and 104, respectively. Inner seals 106 are provided between the interior opening of the packer and the tubing 24. A check valve 42 is adapted to close upon the removal of tubing 24 and henceto control the flow of fluid from producing formation 12.

The apparatus shown in FIGURES 8 and 9 is a simple means for use in practicing this invention to lock casing strings and tubing strings within a well. In this instance a special casing section 110 is adapted, as previously described herein, to be retained opposite a producing formation by cement 112. A string of casing is then locked to the casing section in a sealed relationship.

The upper end of the special casing section in FIGURE 8 includes a circumferential groove 114 and circumferential upper tapered shoulder 116 between which is a relatively straight inner circumferential surface 118. A latching mechanism for attaching a tubing or casing string 120 to the special casing section is included on the lower end of the string 120 and comprises a multiplicity of lefthand threads 122 around its outer periphery. Also included is a ratchet ring 124 internally threaded to fit threads 122 and longitudinally split 132 (see FIGURE 9) for expansion and contraction purposes.

Ring 124 is normally retained within recess 114 and is adapted to interlock and engage with lower ratchet threads 122 of the latching mechanism when lowered within special casing section 110. A tapered shoulder 126 abuts against upper tapered shoulder 116 to stop the downward movement of casing string 120.

Seal 128 seals the space between the end of the cas ing or tubing string 120 and the surface 118 of casing section 110. To remove the casing or tubing string 120, it is necessary merely to lift slightly and rotate the assembly in a clockwise manner to back threads 122 out of split latch ring 124. Fixed key 130 in groove 114 (see FIGURE 9) is adapted to fit within the opening 132 in ratchet ring 124 and hence prevents the split ratchet ring from turning as the casing or tubing string 120 is rotated.

Accordingly, in the operation of the apparatus and method of this invention, a short length of casing is cemented in place opposite a producing formation in a well that either does not need casing extending from the formation to the earths surface or that has the wall of the well stabilized wherever necessary to prevent sloughing or caving or the entry of extraneous fluids into the well.

More particularly, a relatively short length of casing is positioned within the well opposite the producing formation. Ordinarily a string of tubing 24 equipped with an appropriate anchoring mechanism and cementing accessories is then used as described earlier to position and cement the casing in place. The casing and the cement are next perforated to provide communication between the well and the producing formation.

In one embodiment of the invention, communication between the well and the producing formation is established by a wire line perforating gun after the tubing string is removed. The anchoring mechanism can be used to locate or orient the gun if so desired. Thereafter, the production tubing is positioned in the casing and packed off either by a single combined anchoring and sealing mechanism, or preferably by a combination of separate anchoring and sealing devices.

In another embodiment, permanent type well completion techniques may be used to complete or perforate the well, to produce the well fluids, and to perform necessary remedial work.

Although this invention has been described with reference to specific and preferred embodiments, it will be apparent that many modifications can be made Without departing from the spirit and scope of the invention. Ac cordingly, this invention should not be considered to be limited to the embodiment herein described, but instead only by the scope of the appended claims.

What is claimed is:

1. A method of completing a productive formation in a well having competent uncased, walls above said formation comprising the steps of positioning in said well and opposite said formation a section of casing long enough to span the exposed thickness of said formation to the exclusion of at least a portion of the competent walls above said formation,

cementing said casing in said position spanning said formation, and

thereafter completing said well to establish productive fluid communication from said formation to said well through said cement and said casing.

2. A method of completing a productive formation penetrated by a well comprising the steps of,

stabilizing uncased walls of said well above said formation to be substantially competent, casing and cementing said well selectively throughout the vertical length of said formation exposed to said well and to the exclusion of at least a portion of the walls of said well above said formation, and

thereafter completing said well to establish productive fluid communication from said formation into said well across said cement and casing.

3. A method of completing a productive formation penetrated by a well comprising the steps of,

stabilizing the walls of said well other than the walls of said formation to be substantially self competent, lowering into said well a section of easing of length substantially equal to and suflicient to span the vertical length of said formation exposed by said well, positioning said casing opposite said formation, cementing said casing in said position,

releasably and sealably attaching a string of production tubing to said casing, and

completing said well to establish productive fluid communication from said formation into said well across said cement and casing and thence into said tubing for recovery at the surface of said well. 4. A method according to claim 3 wherein said well is completed prior to releasably and sealably attaching said tubing for production of said fluids.

5. A method of completing a well opposite a fluid productive formation wherein at least a portion of the well above said formation is uncased, which comprises the steps of,

releasably assembling a section of rigid casing of length substantially equal to the vertical length of said formation to the lower end of a longitudinal length of tubing,

lowering said assembly by adding additional lengths of tubing to a position opposite said formation and such that said section of rigid casing spans said formation,

pumping cement through said tubing and said assembly into the annular space between said casing and said formation to retain said casing in said position,

releasing said tubing from said assembly, and

withdrawing said tubing to a position whereby said well can be completed to permit production of said formation fluids across said cement and easing into said tubing to the surface of said well, and thereafter completing said well to permit such produc tion of said formation fluids.

6. A method of completing multiple productive formations penetrated by a well comprising,

stabilizing the wall surface of said Well above said formations to be substantially competent,

lowering into said well a section of rigid casing of length substantially equal to but greater than the vertical distance from the top of the uppermost of said formations to the bottom of the lowermost of said formations,

positioning said casing opposite said formations,

cementing said casing in said position,

releasably and sealably attaching permanent type well completion equipment and a separate string of production tubing for each formation to said casing, and

thereafter completing said well to establish separate productive fluid communication from each of said formations into said well across said cement and casing and thence into its respective string of said tubing for recovery at the surface of said well.

7. Apparatus for completing a fluid productive formation penetrated by a well wherein the walls of said well have been made substantially self competent comprising, the combination,

a rigid metallic casing of length substantially equal to the vertical length of said formation and of diameter less than said well,

a tubular conduit extending from a position in releasable connection with a cementing shoe at the bottom of said casing to a position at the surface of said well,

a latch mechanism sealably assembled to said tubular conduit and sealably releasable to the upper end of said casing,

whereby said assembly is positionable opposite said formation to permit cement to be pumped downwardly to the bottom of said casing and thence upwardly into the annular space between said casing and said well wall.

References Cited by the Examiner UNITED STATES PATENTS 526,346 9/1894 Fay 166-21 1,379,656 9/1919 Swan 166-25 1,934,701 11/1933 Edwards et al 166-23 2,156,207 4/1939 Terrill 166-27 X 2,745,495 5/1956 Taylor 166-35 2,766,828 10/1956 Rachford 166-35 X 2,812,958 11/1957 Rogers 285-18 2,986,214 5/1961 Wiseman et al 166-35 3,006,415 10/1961 Burns et a1 166-208 3,055,424 9/1962 Allen 166-21 3,107,930 10/1963 Gibbs et al 285-18 3,131,768 5/1964 Chancellor et al 166-46 CHARLES E. OCONNELL, Primary Examiner.

C. D. JOHNSON, J. A. LEPPINK, Assistant Examiners. 

1. A METHOD OF COMPLETING A PRODUCTIVE FORMATION IN A WELL HAVING COMPETENT UNCASED, WALLS ABOVE SAID FORMATION COMPRISING THE STEPS OF POSITIONING IN SAID WELL AND OPPOSITE SAID FORMATION A SECTION OF CASING LONG ENOUGH TO SPAN THE EXPOSED THICKNESS OF SAID FORMATION TO THE EXCLUSION OF AT LEAST A PORTION OF THE COMPETENT WALLS ABOVE SAID FORMATION, CEMENTING SAID CASING IN SAID POSITION SPANNING SAID FORMATION, AND THEREAFTER COMPLETING SAID WELL TO ESTABLISH PRODUCTIVE FLUID COMMUNICATION FROM SAID FORMATION TO SAID WELL THROUGH SAID CEMENT AND SAID CASING. 